Finding the Third Proportional to 309,470 and 678,676

Step by Step Solution

1. Step 1: Write the proportion equation
   309,470 : 678,676 = 678,676 : x
2. Step 2: Convert to fraction form
   309,470/678,676 = 678,676/x
3. Step 3: Cross multiply
   309,470x = 678,676 × 678,676
4. Step 4: Simplify right side
   309,470x = 460,601,112,976
5. Step 5: Solve for x
   x = 460,601,112,976/309,470
6. Step 6: Final answer
   x = 1,488,354.65